The present invention relates to an improved process for the preparation of 3,3',5,5'-tetratertiary butyl diphenoquinone by the oxidative coupling of 2,6-ditertiary butyl phenol. More particularly the invention lies in the discovery that the catalytic oxidative coupling of 2,6-ditertiary butyl phenol is surprisingly improved if the reaction is conducted in methanol.
The oxidative coupling of phenols, including 2,6-ditertiary butyl phenol is a known reaction. Numerous catalysts and process conditions have been suggested by the art. U.S. Pat. No. 3,555,052, published Jan. 12, 1971, disclosed that reduced noble metals were suitable catalysts for the oxidative coupling of phenols in the presence of oxygen to form diphenoquinone or polyarylene ethers. Suitable solvents included t-butyl and t-amyl alcohol.
3,3',5,5'-Tetratertiary butyl diphenoquinone is a useful antioxidant. It is also a valuable intermediate for the production of 2,2',6,6'-tetratertiary butyl-p,p'-biphenol a useful stabilizer and antioxidant. Furthermore, the 2,2',6,6'-tetratertiary butyl-p,p'-biphenol may be dealkylated to give p,p'-biphenol which is useful in the synthesis of polymers, especially polyesters.